1. Field of the Invention
The present invention relates to powder metal forgings, and, more particularly, relates to minimum flash or flash-free/precision flash powder metal forgings.
2. Description of the Related Art
In the manufacture of powder metal forgings, such as an inner race of a constant velocity joint (CVJ), it is sometimes desirable to provide a through-hardened part directly from the forge press. This requires that the part be directly quenched after the part has been ejected from the forge tooling. In forging such a part, the upper die moves in a downward direction to the lower die to deform the billet, which forms the part. This results in flash forming on the sides of the part where the upper and lower dies meet, which is in an area of bearing races for an inner race of a CVJ. If the part is directly quenched, then the tool flash is in a hardened state. Although hard trimming, which is a method of shearing the flash from the part, is possible, it is not practical because the flash can exceed the hardness of the current trim tooling creating a potentially dangerous situation for the operators and can also negatively impact the quality of the product. That is, the part can break apart during trimming and fly out of the confines of the tooling. Also, the bearing races are precision surfaces and fairly intricate so that they are not very amenable in general to shearing.
A method of forging a CVJ inner race is known whereby a segmented die (6 die segments) is used to form the CVJ inner race using a traditional cold forging technique. However, this technique requires a machine to broach the spline and a relatively long carburization process. Further, there are six vertical witness lines on the part corresponding to the six die segments. Other disadvantages of this method are that it is a relatively complex and expensive tooling arrangement, with a relatively short die life.
What is needed in the art is a powder metal forging and method and apparatus of manufacture which produces a part with a minimum of flash, or no flash, particularly on precision surfaces, and which is compatible with direct quenching after the part has been ejected from the forge tooling.